Proposed studies to elucidate the physiologic basis of immunity in trichinosis are designed in part to test the hypothesis that: (1) physical-chemical changes in lamina propria of the small intestine, (2) alterations in gastrointestinal secretions and gut contents, and (3) alterations in intestinal motility are associated with worm-induced inflammation, and that these alterations interfere with development and/or survival of the intestinal stages of Trichinella, thus are important factors in acquired resistance to infection. A second area of investigation deals with: (1) an assessment of the nutritional requirements of intestinal stages of T. spiralis, (2) physiologic mechanisms involved in the acquisition of nutrients, and (3) sources from which nutrients are obtained. Peroxidase activity in the lamina propria of the small intestine will be measured to determine if the relative activity of this enzyme can be used to quantitatively estimate the degree of inflammation in the mucosa. Enzyme activity will be correlated with the linear distribution of worms in the gut and with various histologic, pathologic and immunologic changes associated with intestinal trichinosis. A factor(s) from disrupted intestinal leukocytes that is lethal for juvenile and adult stages of T. spiralis will be physically isolated, characterized, and examined to determine if it is released from intact cells. The dog will be used as an experimental host to study the relationship of previously observed changes in intestinal motility to diarrhea, intestinal transit time and expulsion of worms from the small bowel. The nutrients utilized by intestinal stages of T. spiralis and the source of these substances will be investigated by examining the digestion, absorption and assimilation of various compounds in vitro. In addition the capacity of worms embedded in intestinal mucosa to assimilate specific compounds and non- metabolizable analogs administered to the host intravenously will be examined. These studies should contribute to a better understanding of host physiologic factors involved in worm attenuation or rejection as well as biochemical and physiologic mechanisms in the parasite that are susceptible to host immune responses, and provide a basis for developing control measures such as vaccines.